Prior to the present invention feed pipe devices were available for dispensing liquid feed components into a cavity for the purpose of coreacting such components. For example, Harkness et al U.S. Pat. No. 4,135,882, shows a nozzle for injecting ingredients into a cavity resulting in the production of urea-formaldehyde foam insulation. A concentric feed pipe is utilized in which the foaming agent is coaxially delivered with respect to an axially extending resin injector. Mixing of the foaming agent takes place in a mixing chamber in the form of a detachable hose away from the nozzle to preclude the nozzle from being clogged. A means is applied to the end of the inner concentric tube to impose a direction and speed on the resin.
A machine for proportioning and mixing two or more liquids and semifluid materials and means for dispensing the resulting mixture is shown by Christensen et al, U.S. Pat. No. 2,802,648. A component of the Christensen et al machine is a device with concentric feed tubes. A screw extruder having an attached eccentric feed element is further shown by Spreeuwers, U.S. Pat. No. 3,148,412.
Adams, U.S. Pat. No. 4,263,166, describes a spray foam insulation gun having a mixing chamber and a resin feed pipe passing concentrically through the mixing chamber. The feed pipe extends beyond a nipple so as to allow resin to impinge with foaming agent at a point beyond the nozzle of the spray gun to prevent clogging of the spray gun nozzle.
A concentric feed element used with a screw extruder is shown by Grubb et al, U.S. Pat. No. 2,863,649. No criticality is shown for the relative location of the concentric tubes and the screws of the extruder. The patent also describes blocking means for the central tube. Steinert et al, U.S. Pat. No. 4,224,282, further shows a concentric feed pipe element for introducing material into a high pressure polymerization autoclave.
Although the aforementioned patents describe feed pipes for dispensing liquids and semi-fluid materials and the simultaneous introduction in a concentric stream into a mixing chamber, there is no teaching of a concentric feed pipe for polymerizing monomers in the molten state at temperatures exceeding 200.degree. C. In addition, there is no teaching in the prior art of a concentric feed pipe device capable of separately introducing highly reactive monomers into an extruder at temperatures exceeding 200.degree. C. Further there is no teaching in the prior art of a concentric feed pipe device which allows for the introduction of liquid monomers at elevated temperatures into a reactor where the feed pipe device must provide means for producing a shield resulting from the flow pattern of one of the reactive fluid monomers to protect the other reactive monomer in the fluid state from undue oxidation prior to contact between the two fluid monomers under reaction conditions in the reactor.